The invention relates to glass melting and in particular to a glass melting furnace and the operation thereof.
In the manufacture of glass in tank furnaces, unmelted bath is fed onto an established bath of molten glass at one end of the furnace where it is melted. The molten glass, which forms from the batch, passes down the furnace from the melting zone through refining and conditioning zones and is drawn off from the other end of the tank to be used in a glass forming process in known manner.
It is difficult in practice to obtain completely homogeneous glass in a glass melting tank. If the glass contains discontinuities of properties, either chemical or physical, it is considered inhomogeneous. Such discontinuities may arise from undissolved solids and gases, differences in composition due to differential glass processing or alternatively variations of physical conditions such as temperature. The difficulty in avoiding inhomogeneity increases at high loads when time and temperature in a particular zone are limited by furnace design and refractory constraints. The glass produced is generally heterogeneous in composition, to a lesser or greater degree, depending upon the efficiency with which melting and subsequent operations are accomplished. Glass varying in composition, forms layers in the furnace these layers being subject to convective and other flows imposed by the furnace operation, design and other physical operations carried out on the glass. In the final product these layers are generally parallel to the glass surfaces but there may be deviation from this parallel state in areas which have been subject to other modifying conditions. Where the layers of inhomogeneity cease to be parallel or continuous to the faces of the glass, optical faults occur.